WHITE PAPER Mining Wireless Network Considerations for Designing a Reliable Network in an Open-Pit Environment
Table of Contents I. Introduction 3 II. Traditional Wireless Network Design 3 III. 3D-P s Network Design Philosophy 3 IV. Connection Management Best Practice 7 V. Conclusion 7 Mining Wireless Network White Paper Page 2
I. Introduction 3D-P has developed a great deal of expertise in designing broadband wireless networks for the open pit environment. 3D-P was first to focus entirely on bringing broadband networks to the mining industry and integrating all of the various third party systems available to the industry onto that network. Some of the lessons learnt, despite going against traditional wireless network design, are critical to the proper design of high availability, high bandwidth networks in the open-pit mining environment. 3D-P s network design focuses on the challenges of this environment, understanding the limitations of commercial off-the-shelf (COTS) technologies and protocols, and delivering a reliable and scalable solution. II. Traditional Wireless Network Design Traditional wireless networks are very RF-centric. Their design principle is simple, and consists of using high power radios and installing them as high as possible so they can reach as far as possible. This solution ensures that fewer infrastructure are required for coverage. Most wireless network vendors follow this model today when deploying broadband wireless networks. When faced with a coverage or network performance issue, the solution is typically to add higher gain antennas, amplify the clients or add more infrastructure. While these solutions will certainly increase signal strengths in some areas, they will also drastically increase the noise floor and cause additional coverage and performance issues. These new issues typically show up in slightly different areas of the network. A vicious cycle then begins, as the network maintainer is tempted to go add additional infrastructure to these new problem areas or get stronger signals from the client devices. III. 3D-P s Network Design Philosophy 3D-P s design philosophy for a reliable wireless network consists of creating individual coverage areas for each access point (AP) and minimizing overlapping zones using terrain, low gain antennas and low power settings. This ensures minimized RF footprint of each AP zone and also helps manage congestion on the wireless medium. In order to create these small RF zones, AP s are mounted low, very near the intended coverage area. The final design is made of many small RF zones designed with the focus of keeping the RF local and maximizing the performance of the protocols. Mining Wireless Network White Paper Page 3
Figure A Figure A provides an example of two access points, each having an appropriate coverage zone. Clients traveling through Zone A will communicate with the AP from Zone A until they reach the overlapping coverage area between Zone A and Zone B. In this area the connection manager will begin to force a scan for a new AP. Once the Zone B AP is received as a stronger signal than the Zone A AP, the client will associate with the Zone B AP. When the client has departed the overlapping coverage area of both AP s, it will be receiving the Zone B AP strong enough that it will no longer search for additional AP s. The communication to the Zone B AP will not be interfered by the communication in the neighbouring Zone A, as the margin between Zone B s signal strength and that of the Zone A AP will be great enough the client will be able to communicate with minimal interference. Mining Wireless Network White Paper Page 4
Figure B Figure B shows an example of a cross section of a pit. In this example, a single AP is utilized to provide a coverage zone over the entire pit. This is often the original deployment plan in many networks. This deployment plan may work well in the instance where few clients will be working in the coverage zone or where the throughput requirement of those clients is very minimal. Figure C As the throughput and client count of the pit increases, the typical solution is the one shown in Figure C. A new AP is added to the pit to provide additional throughput/coverage. However, the interference this new AP creates is often the cause of new trouble. Clients traveling through the pit will perceive a higher noise floor and have trouble communicating clearly with either AP. Often increasing the gain of the antenna on the client is attempted to get communication from this client out of the noise. This again aggravates the problem for other clients in neighbouring pits as their effective noise floor has been increased by the higher gain antenna on this client. Mining Wireless Network White Paper Page 5
Figure D Using terrain and electrical down tilt on one of the AP can provide two nonoverlapping coverage zones for these AP s. This is shown in Figure D. This is a good solution as clients working on the two benches of the pit have a clear choice of AP to utilize for their communication, and the overlapping interference is minimized. Figure E Power can also be utilized to reduce the interference between two adjacent coverage zones. Figure E shows an example of this. Mining Wireless Network White Paper Page 6
IV. Connection Management Best Practice Another important element to obtain maximum performance from a wireless network is in connection management. When client meshing solutions are deployed, such as the Rajant ME4 or the 3D-P Intelligent Endpoint (IEP) with integrated ME4, connection management is managed by the meshing algorithm. However, when standards based 802.11 clients are utilized, connection management must be incorporated. Standard connection management from consumer devices is mainly designed for office or campus style roaming. In these networks, devices attempt to maintain a link to a connected AP as long as possible. Some adjustments to the stickiness of the connection are allowed in an attempt to allow quicker roaming. With these devices roaming events can take over a second to complete. In the mining environment, maintaining a connection to a preferred AP for as long as possible might seem a good idea as it reduces the roaming events, and therefore the roaming time. However, by holding onto a single AP for as long as possible, client bandwidth is sacrificed due to longer distances to AP s. Beyond the distance problem, designing a network for these connections goes against the cellular design that is described in this document, and leads to greater overlap between coverage zones, and increased noise floor and congestion. The overall network performance is decreased. 3D-P has designed significant smarts into the connection management algorithms used on 802.11n equipped IEP s to reduce the roaming time. The IEP uses background scanning to keep a list of available AP s. When an AP provides a significant enough performance increase, the IEP will roam to that AP. Roaming in properly deployed and uncongested networks typically occurs in less than 100ms. In this environment, while roaming does occur more frequently, the required roaming latency is minimized, while the throughput of the IEP and the overall network capacity is greatly increased. V. Conclusion Designing a wireless network for a mine is drastically different than designing indoor networks, or even outdoor urban networks. Serious effort must be spent in minimizing the overlap between AP zones, as well as congestion within these zones. Once the network is properly deployed, ongoing maintenance is required to keep the RF zones optimized as the mine advances, terrain changes, and working areas shift. Mining Wireless Network White Paper Page 7
About 3D-P Focusing on mining since 1996, 3D-P offers a unique solution in the market place by filling the gap between the third party applications, enabling their sharing across the wireless network as well as offering reliable wireless network design, installation, optimization and support. For more information: Email sales@3d-p.com Call +1 403.203.3018 Visit www.3d-p.com 200-8 Manning Close NE, Calgary, Alberta, T2E 7N5 USA Canada South America Australia 2016 3D-P All rights reserved.